Charging with solar panels – a guide for EV owners

Charging your EV with solar panels is an easy way to beat soaring energy prices by reducing your dependency on the grid.

Solar panels offer a cheaper way to charge your EV with renewable energy you generate yourself. The best part? You don’t need a beefy solar installation to do it.

In this guide, we’ll cover everything you need to know about EV solar panel charging so you can drive around on clean, free energy.

Synopsis

Solar panels, also known as photovoltaics (PV) panels, capture energy from sunlight that you can use to charge your electric vehicle.

Depending on how much energy your solar panels generate, you can potentially cut out the grid entirely and charge at 7kW with 100% solar power. However, most domestic solar installations in the UK are between 1kW and 4kW. With a small setup like this, you can either charge your EV slowly with 100% solar or supplement grid energy with solar energy to slash your charging costs.

You need only two things to charge your EV with solar panels: a solar system and a smart home charger with solar integration.

These are the best chargers with solar we’ve reviewed:

• Hypervolt Home 2.0
• Indra Smart PRO
• Zappi v2

All these smart chargers let you tune energy sources in the app, so you can select 100% solar or mixed energy sources. Importantly, all of them let you schedule charging times and view detailed charging session information.

How does solar panel charging work? 

Solar panel charging is easy to wrap your head around.

• Your solar panels convert sunlight into DC electricity
• An inverter, part of your solar system, converts that DC electricity to AC electricity
• The AC electricity is fed to your distribution board to power devices, while surplus electricity is stored in a battery (if installed)
• The smart EV charger takes the AC electricity generated by the solar panels and charges your EV, either directly from the distribution board, or via the battery
• The charger can use 100% solar power to charge an EV, or it can use a combination of solar + grid to achieve the fastest charging speeds
• When AC power flows through the cable into your EV, your EV’s onboard charger converts the AC electricity back into DC electricity.

Here’s a more detailed explanation:

PV panels convert sunlight into direct current electricity. This DC current passes through an inverter which converts it to alternating current that can be used to power home appliances and devices.

For solar EV charging, the DC output from the PV panels connects directly to a bidirectional DC-DC converter. This converter can step up or step down the voltage as needed for charging the EV battery.

During the day when the sun is shining, the solar PV panels generate electricity which provides power to charge the EV through the DC-DC converter. Any excess solar energy gets fed back into the home’s electrical system.

At night or during cloudy weather when solar production is low, the EV can draw supplemental charging power from the grid through a grid-connected inverter.

A key component is the bidirectional DC-DC converter which can switch between buck mode for stepping down voltage when charging the EV battery from the solar panels, and boost mode for stepping up voltage when discharging from the EV battery back to the grid.

The system uses advanced power electronics and control systems to maximize solar PV power harvesting during the day and manage the energy flow between the EV battery, solar panels, and grid optimally based on driving patterns and solar availability.

This allows the solar PV system to power EV charging sustainably utilizing the sun’s energy when available, while still providing grid connectivity as needed. It is a flexible system for integrating solar PV with EV charging infrastructure.

Solar panels for EV charging

You don’t need special solar panels for EV charging. Normal solar panels will do. The most important thing is the energy they can generate as a system and the predicted energy they will generate when it’s cloudy.

Solar installations are rated in kW. The maximum kW generation is only applicable in optimal conditions, i.e. when the sun is shining. Your solar panels will probably reach between 70-80% capacity when it’s cloudy.

So, if you have a 4kW solar system, you will probably generate 3kW of power on a cloudy day, and on a dark day, you might generate 1.5kW or less.

Clearly, this is not sufficient for fast-charging speeds for your EV. However, it is sufficient to supplement your energy consumption while charging, reducing the amount of energy you take from the grid. Or you can charge slowly off-grid.

How many solar panels to charge an EV? 

When installing solar panels to charge an electric vehicle, the number of panels needed depends on several factors.

According to solar energy experts, a solar array with 8-12 high-efficiency panels is typically sufficient to fully charge an average EV battery if that is the sole purpose the panels are serving. However, if you plan to use the solar panels to power your home in addition to EV charging, you may need a larger system with more panels.

The key considerations for determining solar panel requirements for EV charging are:

• EV Battery Size – The larger the battery capacity, the more solar panels you’ll need to charge it. So it’s important to take your specific EV model into account.
• Local Climate Conditions – Solar panels produce more energy in sunnier climates versus cloudier or rainier areas. If you live in an area with limited sunshine, plan for more panels.
• Solar Panel Efficiency – Higher efficiency solar panels can generate more electricity from the same amount of sunlight. Select premium panels to maximize productivity.
• Home Electricity Usage – If your solar panels are powering home appliances and devices in addition to your EV, size the system to produce excess energy beyond your household’s needs.
• Installation Orientation – Optimize solar panel placement to maximize sun exposure. Facing south (in northern hemisphere) is ideal for EV charging.
• Battery Storage – Adding solar batteries allows you to store excess energy for overnight EV charging. But this also increases solar panel needs.

Consult with a qualified solar installer to properly size your system based on these variables. While exact solar panel needs vary, planning for 10-15 high-efficiency panels is a reasonable starting point for powering an EV in most regions.

This Which? guide to the best solar panel brands is a good starting point for your search, with more recommendations at EcoWatch.

How about solar roof tiles instead? The Tesla Solar Roof might be coming to the UK soon (it’s unavailable currently), which can cover your entire roof in solar panel tiles. It can easily generate over 15kW, with each tile producing up to 71.67 watts of energy.

Solar panel installation costs

A 4kW solar system without an energy storage system will set you back around £6,000, while the same system with an energy storage system will set you back around £8,000.

A solar system up to 7kW will set you back up to £11,000, depending on the solar panels you choose and the size of the energy storage system.

A single solar panel costs £350-£500, and you need 12 to 16 panels to deliver 3kW to 4kW.

Another factor that affects costs is your roof’s condition and load-bearing capabilities. Your roof may need work before solar panels can be installed.

If you want to charge your electric car with the Tesla Solar Roof, you’ll need to wait until its UK release, but based on the current exchange rate, the price is around £32,000 for a 2,000 square-foot roof.

Solar panel battery storage

What to do with all the energy you don’t use? You can store it in an energy storage system, a giant battery that captures electricity for you.

An energy storage system lets you charge with solar power at night because it stores electricity during the day.

An energy storage system will increase the cost of your solar installation, but it is the only way to capture the electricity you generate from solar. Without an energy storage system, much of the energy you produce will go to waste!

Here is a brief overview of how battery storage works with solar panels for EV charging:

• Battery storage provides a way to capture and store excess solar energy generated during the daytime, so it can be used later for nighttime EV charging.
• A typical home setup includes solar panels, an inverter, the utility grid connection, and a battery storage unit.
• The solar panels charge the battery storage unit during daylight hours when solar production exceeds the immediate power needs of the home. This stored energy remains in the batteries.
• In the evening when solar production decreases but EV charging needs increase, the stored energy in the battery is discharged to power the EV charger and charge the EV battery.
• This allows the solar energy produced during the day to be “time-shifted” for use at night. Without battery storage, solar panels can only power EV charging during daytime hours.
• Batteries also provide backup power in case of electricity outages. Stored solar energy can be used to charge the EV when the grid is down.
• Popular home battery options include lithium-ion batteries like the Tesla Powerwall or LG Chem RESU. These offer capacities between 5-20 kWh to meet different energy storage needs.
• Batteries have charge controllers to manage charging from solar panels and discharging to power devices and the EV charger optimally.
• While adding battery storage increases upfront costs, it maximizes solar capabilities and savings over time, providing solar power independence and reliability.

Solar battery storage options

Lithium-ion batteries are the most efficient batteries for energy storage. The Tesla Powerwall is the most famous product of its kind, designed specifically for renewables, and it can store up to 13.5kWh and discharge at 5-7kW.

A product similar to the Tesla Powerwall in looks is the Puredrive PureStorage II, which is available in 5kWh and 10kWh capacities. The PureStorage II is British-made and extremely well-regarded among the solar community.

Another option is the GivEnergy LiFePO4, which can store 5.2kWh or 8.2kWh depending on the version, with full renewable integration.

Best solar-integrated smart chargers 

Once you have your solar system, you need a solar-integrated smart charger.

A solar integrated smart charger basically has terminals for a solar or renewable feed, creating a connection between your solar system and EV charger. You can tap into both solar and grid charging by linking the two.

It’s important to point out that you can’t do this with a dumb charger. A dumb charger is a glorified power outlet powered by mains. While you can connect it to your solar system, it will be on or off, with no fine control over the process.

We’ve reviewed and tested plenty of smart home chargers with solar integration. Here are our top recommendations:

Indra Smart PRO

A fantastic smart charger, the Indra Smart PRO can be powered by 100% solar or a combination of solar + grid. It’s available tethered or untethered and charges at speeds up to 7.4kW. It also has the best web app we’ve used to date, Kaluza, which delivers a great user experience and lots of charging data.

Our Indra Smart PRO review gave it 4.5/5.

Hypervolt Home 2.0 

The Hypervolt Home 2.0 is a tethered charger equal to the Indra Smart PRO, although it charges at a slower maximum speed of 7kW. It has something the Indra doesn’t, though – voice control – which is surprisingly handy. It has solar integration as standard, letting you charge with 100% solar (off-grid) or solar + grid.

Our Hypervolt Home 2.0 review gave it 4.5/5.

Zappi v2

No list of solar EV chargers is complete without the Zappi v2, which has smart settings for solar, wind, and micro-hydro generation. It has two ECO charging modes to automatically adjust the charging current in response to on-site generation and household power consumption, charging at speeds up to 7Kw.

Our Zappi v2 review gave it 4.3/5.

Is charging an EV with solar worth it?

Solar panels let you produce clean, off-grid energy. Paired with battery storage, a large enough solar system can power your house indefinitely.

If you already have solar panels, then you have already absorbed the cost of installation so it makes sense to charge your EV with free solar energy. All you need is a smart charger with solar integration and you are good to go.

If you don’t have solar panels, you need to weigh up the cost-benefit.

A solar system will set you back at least £5,000 for a 4kW system, and around £8,000 with battery storage.

Let’s do a quick calculation. A cheap EV tariff costs 5p per kWh. If we divide £5,000 (the cost of a 4kW solar system) by £0.05, we get a sum of 100,000. So, the solar system will pay itself back from EV charging when you consume 100,000kWh.

100,000kWh equates to 300,000 miles at 3 mi/kWh!

A 4kW system generates around 3,400kwh of electricity per year. Clearly, the numbers don’t stack up in favour of solar EV charging for monetary gain, at least in the short term. You would need to rack up some serious miles to make the numbers work.

Of course, solar panels save you money on your total energy consumption, reducing your dependency on the grid in other ways. Even so, estimates suggest you will recoup the installation costs in 11 to 13 years on average.

Charging Your Electric Vehicle with Solar Panels

If you’re an eco-conscious driver looking to go green, charging your electric vehicle (EV) with solar power is a smart way to reduce your carbon footprint.

Installing solar panels on your home allows you to harness the sun’s limitless energy to fuel your EV battery, rather than relying solely on electricity from the grid.

In this guide, we’ll explain how solar EV charging works, discuss the benefits, and provide tips for getting started with your own solar-powered EV charging station.

The technology behind solar charging

The technology behind solar EV charging is relatively straightforward. Solar panels on your roof or property absorb energy from sunlight and convert it into Direct Current (DC) electricity. This DC current passes through an inverter to convert it into the Alternating Current (AC) electricity that powers your home and EV charger.

The inverter ties your solar panel system into the electrical grid. Any excess energy your solar panels produce gets fed back into the grid. And when your solar panels aren’t generating enough, you can draw supplemental energy from the grid. This two-way exchange is called net metering.

For solar EV charging, your inverter directs some of that DC current from the panels directly to your EV charger. This powers up the battery in your EV just like plugging it into a standard wall outlet. Any leftover energy gets sent back into your home’s electrical system.

Benefits of solar EV charging

Charging your EV with solar energy provides a range of money-saving, eco-friendly benefits:

• Lower Electric Bills – Once your solar panel system is installed, the sun provides free charging fuel. This slashes your electric expenses. Any excess power you send back to the grid earns credit on your utility bill.
• Reduce Your Carbon Footprint – Solar charging prevents significant greenhouse gas emissions compared to grid electricity generated by fossil fuels. Driving on sunlight is a clean, renewable alternative.
• Increase Energy Independence – Producing your own power means relying less on the traditional electric grid. Solar charging gives you control over your energy supply.
• Earn Tax Credits & Incentives – Numerous rebates, tax credits, and other incentives are available for installing solar panels and purchasing an EV. These can offset the upfront costs.

• Enhance Property Value – Adding solar panels and an EV charger makes your home more appealing to environmentally conscious buyers. This can boost property value when it comes time to sell.

Getting started with solar EV charging

Installing a solar energy system tailored to your EV charging needs requires careful planning. Follow these tips to get started:

• Assess your power needs – Consider your current electric usage, EV battery size, estimated mileage, and projected charging requirements. This helps determine what size solar array you need.
• Choose your components – Select durable solar panels and mounting equipment along with a grid-tied inverter and smart EV charger compatible with your vehicle. Optimise for efficiency.
• Understand local policies – Research the local laws, permitting processes, and utility policies where you live. Many have regulations regarding home solar systems and grid connections.
• Check available incentives – Look into federal, state, and local incentives, tax credits, rebates, and renewable energy programs available. These can offset system costs.
• Find an installer – Hire a qualified, licensed solar contractor to properly size, design, and install your custom system. Get multiple quotes.
• Consider batteries – Adding a battery storage system allows you to store solar energy and use it anytime for charging, not just when the sun is out. This maximises solar capabilities.
• Monitor your system – Use monitoring software to track solar production vs. consumption. This helps you optimise system performance and efficiency over time.

How to choose a solar pv installer

When selecting an installer for your home solar PV system, battery storage, and EV charger, it is important to do thorough research upfront to find the right provider.

Start by looking for installers in your local area who have extensive experience designing and installing full solar, battery, and EV charging systems, not just solar alone. Check online reviews and ask the installer for references from past customers to evaluate quality of service. Be sure to get quotes from multiple installers so you can compare costs for both equipment and installation.

You want to verify the installer’s qualifications. Choose a licensed, bonded electrician and ensure the installation team has training credentials from leading manufacturers like Tesla and LG.

Ask if they have memberships in any solar industry organisations, such as the Solar Energy Industries Association (SEIA) or North American Board of Certified Energy Practitioners (NABCEP), to confirm their expertise.

When evaluating equipment, the installer should offer high-efficiency solar panels, battery storage units, inverters and EV chargers from reputable brands known for performance and reliability. Panels and electrical components should come with long 10+ year warranties.

The installer should also perform a site evaluation and help customise your system design for optimal sizing and placement.

It is also important to gauge the installer’s responsiveness and service capabilities. You want to choose a company that will provide ongoing system monitoring, maintenance and support after installation is complete. Be sure to understand the full terms of your agreement, including any permits required, incentives available, and payment timeline.

Taking the time to do thorough research and due diligence will help ensure you get the right solar, storage and EV charging system for your needs from a qualified, reputable installer. This will maximise long-term performance and savings.

So, is solar charging worth it? Yes if you want to generate off-grid energy, but not for saving money anytime soon. If you buy a house with solar panels, however, the odds are in your favour.

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